If you are a tech lover, then you might have noticed smartphone circuits, motherboard circuits, laptop's circuit and most of the other electric appliance's circuits are green in colour! But have you ever thought that why these are mostly green in colour? Yah, this question also came to my mind and I researched and found something interesting which I am going to share with you all today.


 Well, this green colour comes from something called solder mask. It is nothing but just a thin layer of polymer applied to the copper traces of a circuit board or in technical terms, PCB. This solder mask is usually made from a substance or liquid. 


You can also know the whole process of creation of a PCB by clicking on this link.

If this masking is not done over the PCB, then there will be a connection between two conductor or nodes or they both may get joined when one or both of them are going to be soldered. This will lead to the failure of the circuit and it may also cause short-circuit. This unintended electrical connection between them is called solder bridge. So it becomes very necessary to avoid these solder bridges. Therefore, in order to avoid this problem, a thin layer or coating is applied between so that while soldering they don't get in contact with each other. The green material is termed as solder mask. This thin layer called solder mask is of four types :
  • Epoxy Liquid
  • Liquid Photoimageable
  • Dry Film Photoimageable
  • Top & Bottom Side Masks
Most of the times, epoxy liquid is used to make solder masks as this is the cheapest among the other three. Epoxy is a thermosetting polymer which is applied on PCB by the process of silkscreening. It is a printing technique woven mesh is used to transfer ink onto a layer except the areas which are impermeable to ink (here, solder mask). For more details, you can also watch about silkscreening and solder-masking practical videos in YouTube.


Silkscreening

Coming to the main point, why these are available mostly in green colour? It is true that some of the PCBs are available in red, blue or yellow colours but they are manufactured in a very less quantity. 

In mass production, green colour masks are only preferred rather than any other colour. This is because green is a contrasting colour in which most of the copper traces can be easily seen by the engineers. The copper traces, the conducting points which are going to be soldered or repaired are easily seen even in low-light also. That's why solder masks are mostly available in green colour. In conclusion, most of the PCB are usually in green colour.  
I hope you guys have understood about this topic and must have fun while reading. Write down your opinion in the comments section and if you found this interesting or helpful, share it with your friends who are being confused about it. Lastly, thanks for reading this article and make sure to turn on your notifications so that you get notified every time I post an awesome new content.